#include <stdio.h>

int main() {
	int d,i,a,b[3]={0};
	scanf("%d",&d);
	scanf("%d",&b[0]);
	for (i=1;i<=d;i++) {
		scanf("%d",&a);
		b[i%2==0?2:1]+=a;
	}
	if (b[2]!=0) {
		printf("2\n%d %d %d",b[0],b[1],b[2]);
	} else if (b[1]!=0) {
		printf("1\n%d %d",b[0],b[1]);
	} else {
		printf("0\n%d",b[0]);
	}
    return 0;
}